Hello I have a Celestron Nexstar Evolution 9.25 with Alt-Azm mount. I would like to have a good diagonal, I was thinking about buying a Televue Everbrite + long adapter for SCT. But I am worried about the clearance with the mount.
With my current diagonal (GSO dielectric) the clearance, when I am pointing to the zenith is small.
Anyone with this telescope has the Televue diagonal + long adapter ? Any recommendations?

I use one of these on my Evolution 9.25". Very easy to lock/unlock a diagonal or other accessory. I think either with this or the other adapter you will have a problem at near zenith. I actually take the diagonal out when the Evo does a Starsense alignment. I think you can also set max/min altitude limits in SkyPortal.

Thanks Junomike, do you think with the "normal adapter" and the TV Everbrite diagonal I will have problems when I point to the zenith.

With my current GSO SCT diagonal the distance between the diagonal and the mount is very small.

Thanks again.

I have the 9.25 Evo and everbrite diagonal. I do need to make sure that I slide the scope as far forward as possible to ensure I get clearance at or near the zenith. And make sure you don’t have any tall eyepieces in the eyepiece tray closest to the diagonal. I usually keep my ethos 13mm in the diagonal and it provides a reasonable counter balance with its 15lb weight. Ok...ok... just a bit of an exaggeration, but it is one heavy beast! hope that helps... Peter A.

I have the Televue Short VB (https://agenaastro.c...r-acs-0004.html) on my SCTs. Its 40mm tall, which is 8mm shorter than the Blue Fireball at 48mm. Once screwed onto my 8" Evol, it has 30mm of internal length for a diagonal's nose piece. I use a Baader 2" diagonal and a 1-1/4" Baader Prism diagonal with a 2" nosepiece. Plenty of inside clearance. Discontinued, but worth the 'wanted' ad on CN......

Now you might consider the WO SCT diagonal. Quite short. As measured by Astroagena, adds ony 14mm from the side of the diagonal to the mating lip of the scope's VB. https://agenaastro.c...agonal-sct.html There's also a twist lock version of it and also just a SCT adapter nose piece.

The shortest possible 2" diagonal is the Baader Maxbright or the Baader Clicklock. The nosepiece can be removed and the diagonal can be screwed directly to the rear cell (or in the case of the 11" and 14" SCTs and the 9.25" Evolution SCT, onto the 3.25" threaded adapter). See these two reviews at my website for a picture:

One caveat; when attached this way the clear aperture is reduced to about 1.5" which will vignette on wider field eyepieces when compared to the full 2" fieldstop available with a 2" diagonal. This article at my website describes what you need for a full 2" clear aperture on 11" and 14" SCTs and on the Evolution's version of the 9.25" SCT:

In my opinion the answer is a counterweight so you can push the OTA more forward in the dovetail and still have it pretty much balanced. I bought this counterweight (see it on the handle of my Mak/Cass which is the same length as a C9.25) I bought for about $20. Sorry to keep posting this but the question keeps coming up. I have an AP 2" Maxbright Diagonal installed so it's pretty much worst case? It clears by about 1/2" at zenith.

After researching this very problem a while back I read a post by a CN member that said "if ever there is anything I want to observe at zenith I just wait an hour or 2 for it to come down". To ease your stress you might want to adopt this philosophy, I did. Remember that nothing stays in any one place very long.

Another thing you may or may not know is that your scope will not stay in balance as you increase the altitude angle. In my case with a ES 2" 18mm eyepiece installed and balanced at horizontal the scope will start to go out of balance at around 30 degree altitude and get worse the more the angle increases. Therefore to reduce the stress on my altitude motor I will typically balance at about 40 degree altitude because most of the things I look at are between 30 and 50 degrees altitude. My scope will pretty much stay in balance over that range.

I did this question to support team of Celestron and they answered me:

Hello

Unless you are using the mount on a wedge for astrophotography, using weights and balancing the optical tube is not required. There's a common misconception that Alt Az mounts need to be balanced with the optical tube. This is not the case. If you are having trouble reaching the zenith, you can slide the optical tube forward on the dovetail with no added stress on the mount.